1. Field of the Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time.
2. Discussion of the Invention
Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.
Devices from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder are well-known in the prior art. Such bladder, or "balloon" type, devices are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry. The devices of the aforementioned patents also disclose the use of fluid flow restrictors external of the bladder for regulating the rate of fluid flow from the bladder.
The prior art bladder type infusion devices are not without drawbacks. Generally, because of the very nature of bladder or "balloon" configuration, the devices are unwieldy and are difficult and expensive to manufacture and use. Further, the devices are somewhat unreliable and their fluid discharge rates are frequently imprecise.
The apparatus of the present invention overcomes many of the drawbacks of the prior art by eliminating the bladder and making use of recently developed elastomeric films, expandable foams and similar materials, which, in cooperation with a base defines a fluid chamber that contains the fluid which is to be dispensed. The elastomeric film membrane or the expandable foam member controllably forces fluid within the chamber into fluid flow channels provided in the base.
The elastomeric film materials used as well as various alternate constructions of the apparatus of the invention are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. Therefore, U.S. Pat. No. 5,205,820 is hereby incorporated by reference in its entirety as though fully set forth herein. Co-pending U.S. Ser. No. 08/046,438 filed by the present inventor on Apr. 13, 1993 also describes various types of expandable cellular elastomers and elastomeric foams used in making the expandable member of various physical embodiments of the invention. This co-pending application is also hereby incorporated by reference in its entirety as though fully set forth herein.
The apparatus of the invention can be used with minimal professional assistance in an alternate health care environment, such as the home. By way of example, devices of the invention can be comfortably and conveniently removably affixed to the patient's body and can be used for the continuous infusion of antibiotics, hormones, steroids, blood clotting agents, analgesics, and like medicinal agents. Similarly, the devices can be used for I-V chemotherapy and can accurately deliver fluids to the patient in precisely the correct quantities and at extended microfusion rates over time.
One of the embodiments of the invention described in this Continuation-In-Part application comprises a rather large infusion device for infusing substantial quantities of fluids into the patient. The device in certain instances can be on the order of eight inches long and four inches wide and, therefore, cannot conveniently be attached to the arms or legs of the ambulatory patient. By providing a relatively soft, pliable device that has a unique, carefully engineered, curvilinear shape such as a kidney shape, a lenticular shape, a mesh of curves, a surface of revolution or any other shape that conforms to the anatomical configuration of the human body, proximate the point of infusion, the device can be comfortably and unobtrusively removably affixed to the patient's upper abdomen. In one form of this novel device, the stored energy source used to expel the fluid from the device comprises a unique expandable sponge-like member. In another form of the invention, the device uses a distendable membrane as the stored energy source.
Another novel form of the invention described in this Continuation-In-Part includes first and second cooperating fluid chambers both driven by unique stored energy sources. This embodiment of the invention permits two or more liquid components to be stored within the device and then controllable intermixed at the time of fluid delivery. Similarly, the multireservoir design permits flushing of one of the reservoirs and the cannula with any selected fluid.